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The present invention relates generally to ventilation of crawlspaces beneath buildings and more specifically to a method for using a modified sill plate as a sill, vent, and drip edge.
Ventilation of the crawlspace beneath a building is imperative to prevent moisture build-up and consequent moisture damage to floor joists, sill plates, rim joists, floor sheathing, girders, posts, and other structural elements exposed to moisture in the crawlspace. Ventilation also helps to prevent the build-up of potentially harmiful or explosive gasses such as methane, natural, ozone, and radon gas. A variety of methods for providing crawlspace ventilation have been used since buildings have been placed upon enclosed foundations. Various regional and national building codes have been enacted over the years which govern the exact amount of venting required for enclosed crawlspaces. Customarily, venting devices for crawlspaces take two forms; the first is a rectangular opening in the concrete, block, brick, or masonry wall hereinafter called a xe2x80x9cfoundation wall.xe2x80x9d The second form is a rectangular opening in the rim joist between the top of the sill, sole, or mud plate hereinafter called a xe2x80x9csill plate,xe2x80x9d and bottom of the floor sheathing.
Although efficiently serving their intended purpose for more than 100 years with only minor improvements, the unsightly partial prior art venting devices nevertheless suffer from a set of drawbacks.
A rectangular foundation vent box is disclosed in U.S. Pat. No. 5,444,947 (Miller) and is typical of the latest design and technology of rectangular vents. Millers"" vent can be used in many applications other than just foundations, due to its unique features. However, it is still a rectangular vent and as such is very difficult to both hide it from view and obtain continuous uniform cross ventilation. Construction standards over the past 50 years have created a standard size of rectangular vents which is on the order of eight inches tall by fourteen inches wide. The design idea is to allow it to fit between framing members, which generally are sixteen inches on center or, greater. This puts them in our direct line of sight with no simple way to hide or conceal them. For example, rectangular vents in the foundation must be located far enough above the existing finished exterior grade to prevent surface water from leaking into the crawlspace, such that there is a plurality of exposed rectangular vent openings along the periphery of the exterior foundation. Furthermore, said vent""s dictate the distance from the finished interior floor to the exterior finished grade. Whereas, building codes dictate a separation from the finished grade to the wood structure above, in the range of six to eight inches, that distance must be increased when using rectangular vents"". Conventional practice is to installed said vents as close to the top exposed portion of the foundation wall as possible, in order to minimize the number of steps to grade.
Additional problems arise with the installation of rectangular vents in foundation walls. They must be coordinated with the form work of the poured-in-place concrete foundation wall, the placement of the rebar steel and, the anchor bolts that tie the sill plate to the foundation. Three things that can and often do go wrong during construction. Furthermore, when vents are installed near the top off the foundation wall, structural concerns arise if point loading occurs in the same spot.
Ideally, rectangular vents must be spaced as uniformily as possible around the entire perimeter of the foundation wall in order to achieve good cross-ventilation of the crawlspace. This will exposed the vent openings in locations that are difficult to conceal. Various attempts to hide them have included the use of plants, decorative vent covers, berming of soil, and pressure treated vent-well boxes. These attempts have proven prohibitively expensive, difficult to install and maintain, and reduce the required trough air flow. Additionally, a vent will compete or conflict with other building elements for the same space, such as; concrete patios"", walkways, decking structures and, beams. This competition will force the grouping of many vents together in the remaining free areas of the building""s perimeter. Effectively dropping the level of required cross-ventilation, thus increasing the risks associated with poorly vented crawlspaces.
Rim vents also follow the same pattern and configuration as foundation vents, offering approximately the same amount of net free air flow. They are commonly made out of wood and more typically found on flat lot buildings where the foundation either is not exposed enough or has already been poured. This puts rim vents higher up the exterior wall assembly than the alternative and does allow a significant reduction in the distance from the finished floor elevation to the finished grade. Unfortunately, rim vents must be installed in the rim, between the floor joists and conflict with the batt insulation which is usually stuffed in that same space. This will effectively reduce or block the rim vent""s trough air flow. Furthermore, by placing a vent higher up the exterior wall assembly its unsightly nature is more visible. This has never been a desirable option.
If these existing venting solutions can be considered prior art, they can both be said to suffer the same fate. They are exposed rectangles which are unpleasant to look at, and offer no effective way hide them from view without impacting venting efficiency. Further, they only function as vents. The current invention seeks to replace them completely.
A sill, sole or mud plate for use along the top periphery of conventional foundations or floor slabs has existed since the invention of lumber. It has also changed little in the past centuries other than the discovery that it must withstand moisture in order to minimize rotting. The definition of a sill plate can be found in any dictionary published. Random House Websters""s Unabridged Dictionary defines a sill plate this way; ""sill (sil), n. 1. A horizontal timber, block or the like serving as a foundation of a wall, house, etc. A conventional sill plate is generally a two inch tall by four or six inch wide piece of rot resistant or chemically treated solid lumber laid flat along the top of a foundation. However, it has no provisions for air transmission at all. Additionally, the conventional sill plate""s exterior lateral face is generally flush with the front exterior lateral face of the foundation and, is designed to accept shear wall nailing of wall sheathing disposed directly above. Therefore, the traditional rectangular shape of a conventional sill plate or prior art beam, precludes any form of integral drip edge extension. It has a solitary function as a standoff attachment between the frame of a wood structure and the foundation wall below.
Accordingly, there exists a need for another natural venting solution which is both uniform along the exterior perimeter of the foundation, while being hidden from view. Combining crawlspace ventilation with a sill plate is unobvious enough to have never been considered prior to this invention. Additionally, the advent of newer composite-wood materials makes this invention more viable.
Continuous horizontal ventilation devices do exist for ventilating attics or walls. Roof eaves and ridges take advantage of openings cut along the horizontal length of said devices to provide a means for allowing uniform trough air. Many patents exist for improving the air flow while reducing pest or water mitigation. Yet, none have the need for high structural compressive strength found along the top of a foundation. Therefore, no embodiment of prior art for horizontal roof or wall ventilators could ever be used in place of a plate or sill in a building. No prior art exists for a structural ventilating device.
The closest prior art invention is found in patent application U.S. 2002/0026762, issued to Charland on Mar. 7, 2002 discloses a grooved Construction Beam. The grooves being filled with air provide vibration dampening and thus reduced noise transmission. The shallow nature of the air-filled grooves also provides thermal insulation as well as minor vent pathways within small enclosed voids like wall stud cavities. The invention relies more upon the concept of ventilation through vapor pressure which drives moisture through objects with low permeability ratings, caused by the difference in air pressure from one environment to the next. The angular grooves merely provide less resistant pathways for the vapor to exit from. This secondary effect is done only in small enough quantities to inhibit rotting of the member itself However, the invention""s main emphasis is providing vibration dampening and thus reduces noise transmission due to impact loads. The grooves are not deep enough nor in the right location to provide adequate trough flow or air for an entire crawlspace. Nor was it intended, ventilation was a side effect of the noise reduction design. This invention broadly covers beams used in any alignment, horizontal or vertical as a method of noise reduction not strictly ventilation. When ventilation is mentioned, it is in combination with xe2x80x9cinsulating advantages.xe2x80x9d The predetermined configuration of groove channels and solid intermediate segments is described as a ratio of groove depth to groove width in the range of 1/6. This ratio is better suited for trapping air than trough air flow. The ratio""s of 1/1 or 1/1.5 with channels perpendicular to an edge are better suited for ventilating. Additionally, this invention discloses the drawbacks of larger, deeper or more frequent grooves in that there are inherent limitations to the soft woods found in conventional construction. Hence, the ratio""s delimiting the invention found within. Furthermore, this invention does not provide either an integral drip edge configuration or screening of the vent channels. The invention does not disclose a method for achieving maximum ventilation while maintaining the structural integrity of the elongated member used in compression and shear found in wall or sill plates.
Functionally, a means for ventilating under floors in a brick building was disclosed in U.S. Pat. No. 718,823 (Darlington) wherein the inventor sought a means to vent all forms of brick buildings with walls of the thickness of four inches and upward consisting essentially, in the use of bricks formed with regular parallel projections on its upper and lower sides forming air passages between bricks at the joints. However, this concept only works with brick buildings and suffers many drawbacks functionally, by codes and construction standards of today. Further, it was never intended to be used as a sill or drip edge. The drawings depict a method of construction wherein the brick wall serves as both the interior and exterior face, uncommon today, and shows no rim board for the floor system. Rim joists, required today, would effectively block such a vent pathway.
Almost all prior art for drip edge/channel systems attempts to solve the trapped moisture problem of various wall systems with some form of applied flashing or apparatus that allows water to escape the siding or wall system in such a manner that channeling water away does not damage the wood sill plates. However, this is not required if the sill plate both functions as a drip edge and is made of a preferred material that resists rotting and insect infestation.
Unfortunately, these items are rarely installed and when they are they can often be installed incorrectly. Unlike the current invention, standard drip flashing requires a higher level of skill for proper water mitigation away from the building. The proposed invention is as easy to install as the original wood sill plate. Thus, effectively making base sidewall flashing obsolete.
None of the above inventions and patents, taken singly or in combination, is seen to describe the instant invention as claimed.
The present invention provides the function of a crawlspace ventilation apparatus with the utility of a conventional sill plate configured to function as a drip edge for the exterior walls of the building. It will also serve as an obvious place to start the wall sheathing. The combination of three building elements into one novel product is always considered an improvement in the construction industry.
The plurality of continuous lateral slot channels incorporated into the entire length of the base of the sill plate, will allow trough flow of air, naturally from the exterior atmosphere to the interior atmosphere and back out again. Creating a means by which continuous and uniform ventilation is achieved.
It is an object of the invention to provide a slightly thicker sill plate, from the slotted channel base to the opposing top face. Thus, allowing for enough integral shear nailing surface of the wall sheathing to the lateral edge of the sill plate, in addition to adequate vent channel openings. The preferred embodiment will have a horizontally extending vent hood, integral to the sill plate, that serves as both a termination base for the exterior wall sheathing, and an integral sloping drip edge designed to channel water away from itself, the wall, and the foundation.
Accordingly, it is a principal object of preferred invention to provide a minimal architectural element along the base of the exterior walls that conceals the vent slots from view, while serving as a base and drip edge. Another embodiment would be to leave the integral sill edge off the invention to allow a reduction in the material and the inclusion of a standard sill on top of the ventilator portion.
Furthermore, by using the sill location as a vent, there will be no conflict with floor joist insulation. Conventional floor joists rest upon the top surface of the sill plate with batts of insulation stuffed between the joists, extending no farther down than the base of the floor joists or top of sill plate. Therefore, a ventilating sill plate can maintain a clear, unobstructed path, unencumbered by insulation, for trough air flow of the crawlspace.
It is another object of the invention to both vent between the sill and the foundation to which it is attached, and drain water away from the foundation wall. The invention reduces the risks of moisture accumulation at this junction, with consequent potential rotting of the building frame.
Still another object of the invention is to be manufactured from a material approved to be in direct contact with masonry or soil. Materials can be but are not limited to, pressure or chemically treated woods, cedar or other rot resistant species of wood, or engineered polymer-fiber composites tested and approved for such use. The present invention can take advantage of any combination of these technologies. The preferred embodiment would be a composite material.
It is yet another object of the invention to provide a shield or barrier from pests and insects, between the exterior slotted vent openings and the interior of the crawl space, by means of a mesh screen. A wide variety of materials can be used for the screening depending on the type of pest or insects in the region, and the local weather conditions. The base slot channels make a continuous mesh simple and easy to install, with the weight of the structure helping to hold it in place.
According to a particularly preferred embodiment of the invention, using a synthetic lumber, which is a substitute for wood in areas where wood can deteriorate quickly due to environmental conditions. One such product manufactured under the trademark TREX, by Trex Company, LLC, Winchester, Va., consists of a polyethylene-wood fiber blend which is extruded into board dimensions for decking and code approved sill plate substitutions. Testing and approvals have already been secured by companies like Trex, for using their product as a sill plate in direct contact with the ground or concrete.
Another advantage of the present invention in one embodiment where the sill is manufactured from a polymer-fiber composite, is the superior lateral strength in transferring the shearing forces of the wood structure above, into the foundation. This embodiment will not fracture like conventional wood. Its plastic nature allows for greater bending stresses before failure. A feature which is usefull in higher wind or earthquake prone areas.
Additionally, the preferred embodiment of this invention utilizing a polymer-fiber composite, incorporates all the benefits of durability, termite, and rot resistance. The water impermeability feature of polymer-fiber composites, allows the current invention to act as a building drip edge for the sheathing and siding, whereas conventional wood sill plates absorb too much moisture to be effective as a drip edge. Normally, the sill plate does not extend beyond the face of the foundation, yet this invention must extend out far enough to allow the prescribed amount of net air flow, facing a downward direction. Thus the form of concealing the vent slots functions as an integral drip edge by design.
Furthermore, the costs of milling the proposed shape would be more expensive in wood than the extrusion or molding process favored by the artificial or engineered wood industry.
It is yet a further object of the invention to maintain, in any form, methods for manufacturing and milling of lumber or engineered wood products, through a set of easy, efficient and relatively inexpensive steps so as to allow manufacturing of the proposed sill vent effective in accomplishing its intended purposes.
The particular advantage with this inventive sill over traditional drip channels or foundation vents, is that installation is exactly the same as traditional wood sill plates, while making it possible to dispense partially or completely with traditional rectangular vents and drip channels.
Another embodiment of this invention is differently configured and simpler. By simply removing the drip edge hood extension, the front edge of the sill is flush with the front face of the foundation wall, as in traditional sill plates. This opens the vent slotting to view from the exterior, but that may be preferred in some forms of building sheathing and fascia, like brick or stonework. Where the siding or fascia is installed in front of the vent slots concealing them from view, allowing enough space between the material and the vent openings to maintain trough air flow.
While my above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible.